Apparatus for and method of forming post seal for lead-acid cell

ABSTRACT

A post seal design for a lead-acid cell utilizes the combination of a one-piece flexible seal and a post coated with a relatively rigid adhesive coating to inhibit acid leakage. Additionally, the post may contain a number of grooves in its periphery to further inhibit leakage resulting from corrosion of the post. The coating may be applied to the post prior to the installation of the flexible seal thereon, or alternatively, the flexible seal may be used as a mold to cast the coating in place on the post after the installation of the flexible seal.

United States Patent [151 3,652,340

Sharpe et al. [4 Mar. 28, 1972 [54] APPARATUS FOR AND METHOD OF [56]References Cited gggllt'ilNG POST SEAL FOR LEAD-ACID UNITED STATESPATENTS 2,892,006 6/1959 Belove ..l36/i68 [72] Inventors: Louis H.Sharpe, Morris Township; Jayant 3,434,883 3/1969 Babusci at alm H R.Shrofl, Morristown; Frank J. Vaccaro, Parsippany, all of NJ.

Primary ExaminerDonald L. Walton [73] Assignee: Bell TelephoneLaboratories, Incorporated, Att0rneyR. J. Guenther and Edwin B. CaveMurray Hill, NJ.

[57] ABSTRACT [22] Filed: Dec. 29, 1969 A post seal design for alead-acid cell utilizes the combination [2]] Appl' 888388 of a one-pieceflexible seal and a post coated with a relatively Related ApplicationData rigid adhesive coating to inhibit acid leakage. Additionally, thepost may contain a number of grooves in its periphery tocommuatlon-m-part 0f Jime- 9, further inhibit leakage resulting fromcorrosion of the post.

1969, abandoned The coating may be applied to the post prior to theinstallation of the flexible seal thereon, or alternatively, theflexible seal US. may be used as a mold to cast the coating in place onthe post [51] int. Cl. v i ..H01m 1/02 after the instanation f theflexible sea].

[58] Field ofSearch ..l36/l68, 176

6 Claims, 3 Drawing Figures APPARATUS FOR AND METHOD OF FORMING POSTSEAL FOR LEAD-ACID CELL This application is a continuation-in-part ofcopending application, Ser. No. 831,611, filed June 9, 1969, nowabandoned.

BACKGROUND OF THE INVENTION 1. Field of the Invention This inventionrelates to lead-acid storage batteries and more particularly to a newpost seal design for such batteries.

2. Description of the Prior Art Significant numbers of lead-acidbatteries, representing an investment of millions of dollars, are usedfor standby power in the telephone plant. Because of the largeinvestment and very limited use, such batteries should have a usefullife of several years.

A major problem area of lead-acid batteries with extended lives is acidleakage around the battery posts. The leakage may result fromelectrolyte being splashed or thrown during handling of the battery,from gassing during overcharge of the battery, from capillary rise ofthe electrolyte or from the growth of corrosion products along thebattery posts. The leakage from the growthof corrosion products alongthe post is especially prevalent on the positive post where lead oxideproducts form or grow as the cell ages.

None of the presently used post seals are completely satisfactory. Mostof these seals are rigid type seals which allow no movement between thepost and the cover. Thus, the seal may be easily broken due to stressesand movements caused by handling of the battery. Likewise the growth ofthe positive plates and positive post upon aging causes relative motionbetween these parts and the cell cover which tends to break a rigidseal.

Another disadvantage of most presently used seals is the short seallengths-usually less than one-half inch. This short seal length can morereadily be breached by the acid than could a longer seal length.

Presently used seals do not provide an effective means of inhibiting thegrowth of corrosion along the battery posts.

Still another disadvantage of most presently used seals is that few ofthese seals provide a redundant sealing system. A failure of the primaryseal results in extensive leakage problems very quickly.

A significant improvement in the design of post seals for lead-acidbatteries was disclosed in US. Pat. No. 3,434,883, issued Mar. 25, 1969,to L. D. Babusci, B. A. Cretella, D. O. Feder, and D. E. Koontz, and indivisional application thereof, Ser. No. 778,900, filed Oct. 3, 1968,and issued Jan. 20, 1970 as Pat. No. 3,490,954. This patent disclosed athree-piece, flexible seal which provided an increased seal length,flexibility to accommodate motion and growth of the plates and postrelative to the cover, and a redundant sealing system. A majordisadvantage of this seal, however, is the difficulty of assemblybecause of the three-piece design. Further, this post seal designprovided no adequate sealing means between the post and its surroundingshrink tube to control the growth of corrosion products along the post.

Accordingly, it is an object of this invention to improve the post sealof lead-acid cells to eliminate leakage of acid around the posts.

Another object is to simplify the design of the post seal of lead-acidcells to facilitate the assembly of such seals.

SUMMARY OF THE INVENTION The foregoing objects and others are achievedin accordance with the principles of the invention by the use of anelectrode post which is coated with corrosion-inhibiting material and aone-piece flexible tube or seal surrounding the post and also connectedto the cell cover. The post is coated with an appropriate material suchas a relatively rigid epoxy resin. The fully extended one-piece flexibletube is then slightly inflated by a pneumatic tool and is then slippedonto the coated post. When the air pressure is removed, a portion of thetube then grips the post with a shrink fit, thereby forming a gastightseal with the coated post to prevent acid leakage from splashing,gassing or capillary action. The coat of material on the post preventsleakage from the growth of corrosion. The remaining portion of theflexible tube is turned inside out and fastened over the exteriorsurface of a cylindrical flange which protrudes from the cover andsurrounds the post, thereby forming a gastight seal with the cell cover.In essence, the flexible tube provides the liquid electrolyte and gasseal while the coat of material on the post provides the post corrosionseal. A corrugated rubber gasket formed as an integral part of the tubeon its exterior surface forms a close fit with the interior of theprotruding cover flange to act as a secondary liquid electrolyte and gasor vapor seal. The portion of the tube which is turned inside out hassufficient flexibility to accommodate any motion between the plates,post, and cover. Additionally, the one-piece flexible tube or sealeliminates the necessity for joints which are required by seals withmultiple parts.

As an alternative to coating the post with the epoxy resin prior to theinstallation of the flexible tube, the tube may be installed on the postand used as the mold for casting the resin about the post. This methodinsures the integrity of the joint between the flexible tube and thepost coating as well as the integrity of the joint between the postcoating and the post itself.

BRIEF DESCRIPTION OF TI-IE DRAWINGS A more complete understanding of thepresent invention and'the objects and features thereof may be gainedfrom the following detailed description and accompanying drawings, inwhich:

FIG. 1 is a sectional view of the fully extended one-piece flexibletube;

FIG. 2 is a sectional view showing the tube assembled on the coated postin the lead-acid battery; and,

FIG. 3 is a sectional view of a fully extended one-piece flexible tubewhich could advantageously be used as a mold for casting the postcoating after the tube is installed on the post.

DETAILED DESCRIPTION FIG. 1 shows a sectional view of a one-piece postflexible tube or seal 1 0 I comprising a sleeve portion 10, a flexiblebag portion 11 and a corrugated gasket 12 formed on the exterior surfaceof the sleeve 10. The seal 1 0l may be made from any appropriateacid-resistant material such as butyl rubber, silicone rubber, orpolyethylene. The interior diameter of the sleeve portion 10 of the tube1111 is made slightly smaller than the diameter of the coated batterypost to insure a shrink fit upon installation.

The flexible seal 1 01 may advantageously be used with a battery postwhich has received an appropriate coating of acid-resistant,corrosion-inhibiting material in some operation prior to theinstallation of the seal 113 over the post as is explained in thefollowing sections.

FIG. 2 shows a sectional view of the one-piece flexible tube 1111assembled on a coated post in the lead-acid battery. The battery post 13exits the cell through an opening in the battery cover 14. The openingis surrounded by a substantially cylindrical flange 15 which protrudesdownward into the cell. The post 13 is coated with an acid-resistant,relatively rigid adhesive material to fon-n a coating 16. Oneappropriate material is a rigid epoxy resin coating 16 which controlsthe growth of corrosion products on the post 13 and thus inhibits acidleakage due to corrosion along the post. The coating 16 also forms agood surface with which the sleeve 10 of the flexible seal can form agastight seal to prevent leakage of liquid electrolyte and gases fromsplashing, gassing, or capillary action. Depending in part upon thedesign life of the cell, a suitable oxidation-resistant grease may beused for coating 16 instead of the epoxy resin. Although corrosion isprimarily present on the positive post, the coating 16 mayadvantageously be used on both the positive and negative battery posts.The coating 16 may be applied in some operation prior to insertion ofthe post 13 in the cover 14, and prior to the installation of seal 11 onthe post.

- A number of grooves 17 may be formed around the periphery of the post13 and filled with the coating 16 to further inhibit the growth ofcorrosion on the post 13. The grooves 17 inhibit the growth of corrosionproducts by increasing the effective path length that the corrosion musttravel and by developing compressive restraints on the corrosionproducts which are less dense than the metal being corroded. The groovesmay have various configurations. However, configurations having sharpcomers or angles appear to be most effective.

The fully extended tube is inserted, flexible bag portion 11 first, overthe coated battery post 13. Because the coated battery post 13 isslightly larger than the inside diameter of the sleeveportion 10 of theseal l l, the post 13 acts as a stopper on one end of the sleeve 10. Thesleeve may be slightly inflated and easily slipped into position on thecoated post 13. When the air pressure is released, the sleeve 10 forms ashrink fit with the coated post 13, thereby creating a gastight sealwhich prevents acid from leaking between the sleeve 10 and the post 13because of splashing, gassing or capillary action. Although it is notrequired under normal conditions, an appropriate adhesive, such as butyladhesive, may be applied to the inner surface of the sleeve 10 and thecoated post 13 to further insure a gastight seal and to furtherstabilize the position of the sleeve 10 on the coated post 13.Alternately, ribs could be provided on the post 13 to fix the sleeve 10in position and prevent any slippage.

After the sleeve portion 10 of the seal 111 is positioned on the post13, the flexible bag portion 11 is reversed or turned inside out andslipped over the exterior surface of the protruding cover-flange whichsurrounds the post 13. The bag 11 is fastened to the flange 15 by asuitable adhesive 18 such as butyl adhesive to form a gastightacid-resistant seal which prevents acid from leaking between the sleeve10 and the cover 14. The bag 11 has sufficient flexibility toaccommodate any relative motion between the post 13 and the cover 14caused by handling or by growth of the battery grid plates or electrodepost upon aging. The corrugated gasket 12, formed as an integral part ofthe exterior surface of sleeve 10, forms a seal with the interiorsurface of the flange 15. Thereby a secondary seal is formed to furtherguard against acid leakage between the sleeve 10 and cover 14.

As previously mentioned, an alternative to casting the epoxyresin'coating 16 about the post 13 prior to installation of the flexibletube is to use the flexible seal itself as a mold for casting the resincoating. FIG. 3 shows a flexible tube or seal l 02 which mightadvantageously be used for such an application.

Tube l 0 2 comprises a sleeve 19, a flexible bag section 20, and acorrugated gasket 21 formed on the exterior surface of sleeve 19 whichare somewhat similar to analogous parts of tube Q11.

Tube m also has a number of spaced projections 22 on its interiorsurface which space the tube Q from the post 13 upon installationthereon. At the bottom end of the sleeve 19 is a circumferential rib 23around the periphery of the interior surface of the sleeve 19. The rib23 forms a seal around the post 13 when the tube LQZ is installedthereon for purposes to be described later.

Prior to installation on post 13, the interior surface of tube isthoroughly cleaned with a suitable cleaner to insure a good bondingsurface. A commercially available alkaline laboratory cleaner, such asthat available under the trademark of ALCONOX from Alconox, Inc., mayadvantageously be used for such cleaning. After being cleaned, theinside surface of tube M may advantageously be coated with a butyladhesive to insure a'better seal from the operations which subsequentlyfollow. Tube 12 is then installed over post 13. A suitable resin, suchas an epoxy resin, to form coating 16 is then forced into the voidsbetween the tube m and post 13, i.e., into the interstices betweenprojections 22. Rib 23 dams this resin and keeps it from leaking outprior to setting. The resin might advantageously be forced into thevoids between tube m and post 13, through a hypodermic-type injectorwhich is inserted through sleeve 19 just above rib 23. This method ofinjecting the resin insures that all of the air is swept out of thevoids and replaced by resin to insure an integral joint. After the voidshave been completely filled with resin the apparatus is heated to theproper temperature for setting the resin to form coating 16. Theresulting coating 16 has very strong adhesive joints with both the post13 and tube 1L2 to insure no acid leakage either from the growth ofcorrosion along the post 13 or from the escape of liquid or gas from thecell.

After the coating 16 has been properly cured, the apparatus is insertedinto the cover 14 of the battery. The flexible bag portion 20 of tube 10g is then turned inside out and fastened over the exterior surface offlange 15 in the same manner as the bag portion 11 of tube m1 shown inFIG. 2. Also, gasket 21 forms a secondary seal with the interior surfaceof flange 15 in the same manner as the gasket 12 of tube m..

it is to be understood that the embodiment of the post seal shown hereinis merely illustrative of the principles of the invention. Variousmodifications thereto may be made by those skilled in the art withoutdeparting from the spirit and scope of the invention.

What is claimed is:

1. A lead-acid battery comprising, in combination:

a battery receptacle;

a cover for said receptacle having at least one opening therein, saidcover having a flange depending therefrom into said receptacle andsurrounding said opening;

an electrode post mounted within said receptacle and extending throughsaid opening; and

I sealing means for preventing leakage of electrolyte around said post,said sealing means including:

a first seal for preventing said leakage from growth of corrosion alongsaid post comprising a tightly adhering coating of acid-resistantmaterial covering said post, said coating being located adjacent saidopening and extending along a substantial length of said post withinsaid receptacle; and

a second seal for preventing said leakage of said electrolyte in liquidand gaseous form comprising a tubular structure of acid-resistant,resilient material having first and second sections, said first sectionsurrounding said post and forming a shrink fit, vapor-tight joint withsaid coating along substantially the entire length thereof, said secondsection surrounding said flange and forming a vapor-tight joint aroundthe entire periphery thereof.

2. Apparatus in accordance with claim 1 wherein said first section ofsaid structure includes:

a plurality of projecting members on the interior surface thereof forspacing said first section from said post so that a resin ofacid-resistant material can be injected therebetween; and

a circumferential rib around the periphery of the inner surface on oneend thereof, said rib forming a liquid-proof seal with said post aroundthe entire periphery of said post to prevent leakage of said resin, sothat said second seal can be used as a mold for forming said coatingabout said post.

3. Apparatus in accordance with claim 1 wherein said post includes atleast one groove around the periphery thereof, said coating filling saidgroove so as to increase the effective path length presented by saidcoating to said growth of corrosion thereby to further reduce leakage ofelectrolyte.

4. Apparatus in accordance with claim 1 wherein said first section ofsaid structure includes a circumferential gasket formed about theexterior surface thereof, said gasket contacting the interior surface ofsaid depending flange around the entire periphery so as to form asecondary seal for preventing leakage of liquid and gaseous electrolyte.

5. The method of making a lead-acid battery including a receptacle, acover for said receptacle having at least one opening therein surroundedby a flange depending from said cover, and an electrode post mountedwithin said receptacle and extending through said opening, comprisingthe steps of:

surrounding a substantial length of said post by a first portion of atubular structure of resilient, acid-resistant material so that saidfirst portion is spaced from said post by protruding members on theinner surface of said first portion; 7

filling the space between said post and said first portion with theresin of an acid-resistant material; curing said resin to form a tightlyadhering coating about said post which substantially reduces the growthof corrosion along said post, said coating adhering to said firstportion and forming a vapor-tight joint therewith so as to create asealed post assembly;

inserting said sealed post assembly into said receptacle and positioningsaid first portion adjacent said opening so that said first portionextends a substantial distance within said receptacle; and

attaching a second portion of said tubular structure around the entireperiphery of said flange to form a vapor-tight joint therewith so thatleakage of electrolyte from said battery is eliminated.

6. The method of forming a post seal for a lead-acid cell including anelectrode post and cover, comprising the steps of:

surrounding said post with a substantially tubular structure ofacid-resistant, resilient material, said structure having said first andsecond sections;

filling the space between said first section and said post with theresin of an acid-resistant, adhesive material, said filling stepincluding inserting a hypodermic-type injector through said firstsection and injecting said resin into said space through said injectorthereby to ensure that said space is completely filled with said resin;

curing said resin to form a coating of said acid-resistant adhesivematerial on said post, said coating forming substantially continuousvapor-tight joints with said post and said first section;

inserting said coated post into said cover; and

attaching said second section to said cover to form a vaportight jointtherewith, whereby acid leakage around said post is substantiallyeliminated.

2. Apparatus in accordance with claim 1 wherein said first section ofsaid structure includes: a plurality of projecting members on theinterior surface thereof for spacing said first section from said postso that a resin of acid-resistant material can be injected therebetween;and a circumferential rib around the periphery of the inner surface onone end thereof, said rib forming a liquid-proof seal with said postaround the entire periphery of said post to prevent leakage of saidresin, so that said second seal can be used as a mold for forming saidcoating about said post.
 3. Apparatus in accordance with claim 1 whereinsaid post includes at least one groove around the periphery thereof,said coating filling said groove so as to increase the effective pathlength presented by said coating to said growth of corrosion thereby tofurther reduce leakage of electrolyte.
 4. Apparatus in accordance withclaim 1 wherein said first section of said structure includes acircumferential gasket formed about the exterior surface thereof, saidgasket contacting the interior surface of said depending flange aroundthe entire periphery so as to form a secondary seal for preventingleakage of liquid and gaseous electrolyte.
 5. The method of making alead-acid battery including a receptacle, a cover for said receptaclehaving at least one opening therein surrounded by a flange dependingfrom said cover, and an electrode post mounted within said receptacleand extending through said opening, comprising the steps of: surroundinga substantial length of said post by a first portion of a tubularstructure of resilient, acid-resistant material so that said firstportion is spaced from said post by protruding members on the innersurface of said first portion; filling the space between said post andsaid first portion with the resin of an acid-resistant material; curingsaid resin to form a tightly adhering coating about said post whichsubstantially reduces the growth of corrosion along said post, saidcoating adhering to said first portion and forming a vapor-tight jointtherewith so as to create a sealed post assembly; inserting said sealedpost assembly into said receptacle and positioning said first portionadjacent said opening so that said first portion extends a substantialdistance within said receptacle; and attaching a second portion of saidtubular structure around the entire periphery of said flange to form avapor-tight joint therewith so that leakage of electrolyte from saidbattery is eliminated.
 6. The method of forming a post seal for alead-acid cell including an electrode post and cover, comprising thesteps of: surrounding said post with a substantially tubular structureof acid-resistant, resilient material, said structure having said firstand second sections; filling the space between said first section andsaid post with the resin of an acid-resistant, adhesive material, saidfilling step including inserting a hypodermic-type injector through saidfirst section and injecting said resin into said space through saidinjector thereby to ensure that said space is completely filled withsaid resin; curing said resin to form a coating of said acid-resistantadhesive material on said post, said coating forming substantiallycontinuous vapor-tight joints with said post and said first section;inserting said coated post into said cover; and attaching said secondsection to said cover to form a vapor-tight joint therewith, wherebyacid leakage around said post is substantially eliminated.